According to U.S. Sen. Michael Bennet’s website, reforming immigration policy and combatting climate change are two of his key legislative goals.

But there is no evidence that the senator sees any connection between them, despite the fact that the U.N.’s Intergovernmental Panel on Climate Change has identified population growth as one of the two key drivers of global warming, and that most of the increase in U.S. greenhouse gas emissions in the past two decades has occurred due to population growth, while per capita emissions have remained relatively flat.

While they have so far neglected to provide hard numbers, the Senate Gang of Eight proposes two changes that would greatly increase America’s population. First, an immense amnesty covering up to 12 million illegal immigrants, who would then be able to bring in tens of millions of relatives under current “family reunification” rules. Second, a huge increase in legal immigration, among both unskilled and skilled workers.

Together, these changes could increase immigration into the U.S. by 1 million annually, to as many as 2.25 million people annually. Using Census Bureau forecasting methods, here are projections for U.S. population growth during this century:

• 250,000 annual immigration = 379 million in 2100;

• 1.25 million annual immigration = 524 million in 2100; and

• 2.25 million annual immigration = 669 million in 2100;

As can readily be seen, even at present immigration rates, the U.S. is on track for huge population increases during the 21st century, from a current population of 315 million to 524 million people by 2100. It is not clear how such increases can be accommodated in an ecologically sustainable manner.

Further increasing America’s already generous immigration rates, as proposed by Sen. Bennet, could add another 145 million people to our population. That increase itself is equal to almost half our current population. It would ensure that the U.S. more than doubles its total population by 2100, to 669 million people.

And make no mistake: Immigrants are not coming to the United States to remain poor. Those hundreds of millions of new citizens will want to live as well and consume energy at the same rates as other Americans.

All this suggests some obvious questions: What climate change mitigation measures does Sen. Bennet plan to put forward that could possibly equal the increased greenhouse gas emissions we would lock in by adding 145 million more new citizens to our population?

Have any of the senator’s environmental aides “run the numbers” on what his immigration proposal would mean for U.S. climate change mitigation efforts (or their impact on other environmental problems, such as urban sprawl along the Front Range, or water conflicts between Colorado and other Southwestern states)? If not, how serious is Sen. Bennet about addressing global climate change?

Finally, why should Coloradans put solar panels on our houses, purchase more fuel-efficient vehicles, tax ourselves to support mass transit, or do any of the 1,001 things environmentalists typically advocate to deal with climate change, if our elected officials are just going to negate those efforts by importing hundreds of millions more people into our country?

Answering these questions should be part of the national conversation on comprehensive immigration reform. That conversation will hardly be “comprehensive” if it fails to address them.